Add additional parameters to the DeepSpeedStrategy

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### Description & Motivation

Related: #12820

Actually, the description is pretty much the same of that issue:
> .. a few more parameters have become available for DeepSpeed including ignore_unused_parameters (the opposite of find_unused_parameters for DDP).
>
> https://www.deepspeed.ai/docs/config-json/#zero-optimizations-for-fp16-training
>
> Integrate ignore_unused_parameters, round_robin_gradients and stage3_gather_16bit_weights_on_model_save into the Strategy.

### Pitch

An ultimate solution might be to allow `.json`-based configuration as done in Deepspeed, but adding more parameters would be a great remedy at least in the short term. Personally I'm interested in `ignore_unused_parameters`, which might become more and more useful as people train multimodal LLMs (related: https://github.com/huggingface/accelerate/issues/2194)

### Alternatives

Implementing this on my Lightning fork and use it.

### Additional context

_No response_

cc @borda @awaelchli

Start by locating the DeepSpeedStrategy entry point and read related issue #12820 alongside the DeepSpeed configuration documentation linked in the issue. Done means the Strategy supports ignore_unused_parameters, round_robin_gradients, and stage3_gather_16bit_weights_on_model_save, with tests covering the added parameters.

Written by the indexing model from the issue text.